Carrier transport systems include carriers for transferring articles contained therein between carrier transport stations. These systems provide a carrier track to which carriers are attached. If such carrier tracks traverse sections of a building wherein the sections are designed with fire inhibiting building walls to inhibit the spread of fire and fire byproducts, then these openings may allow spreading of a fire or fire byproducts from one side of the fire inhibiting wall to the other. Fire doors are commonly provided in these openings.
For such carrier transport systems having carrier tracks located near the ceiling so that carriers hang from the tracks, it is beneficial to provide up closing fire doors. However, since such fire doors can be of substantial weight, if a motor is used to close an up closing fire door, then the minimum required rate of speed at which the fire door must close for safety standards necessitates a large, relatively expensive motor. Further, if a motor is used, electrical power must be available during a fire to close the fire door. This is not a fail safe method. Counterweights could be used to close the fire door, as done in this invention. Then additional controls may be required to prevent the fire door from slamming closed and thereby disturbing building occupants during periodic fire door testings.
Thus, it would be advantageous to have an up closing fire door that meets appropriate safety standards in terms of speed of closing and yet does not slam while closing. It is further advantageous not to require electrical power to close the fire door and use a relatively small motor to execute the act of opening the fire door, a non-critical function with regard to safety.